Just some notes on client storage.
Cookies
Text. Sent with each request.
localStorage
localStorage persistent to a small maximum, something like 5MB. Local storage keeps things stored 'forever'.
Good for username fields, preferences for website display or something like that.
sessionStorage
sessionStorage is based upon the tab session - 3 tabs equals 3 different sessions. Doesn't send your session id automatically like with a cookie. Data is persisted for the lifetime of the session.
Storage events
Both session and local storage, as soon as you CRUD something, it will fire off an event. you can listen to these events in any browser or tabs. So say you remove from tab one, then the other tabs will get those events - cross window messaging.
LevelDB
Coming soon.